This invention relates generally to gas-liquid and gas-slurry reactions, and more particularly to a method of and apparatus for creating sub-micron bubbles in liquids and slurries.
Gas-liquid and gas-slurry reactions present unique problems not found in single phase reactions. The rate and efficiency of a gas-liquid reaction is dependent on the amount of contact between the gas and the liquid. The contact occurs at the interface of the liquid and the gas and is, therefore, dependent upon the surface area of the gas bubbles in the liquid. For a given amount of gas, the smaller the bubbles, the greater the surface area. It is therefore advantageous to produce smaller bubbles in order to achieve the best reaction efficiency.
Despite the advantages inherent in producing minute-sized bubblesxe2x80x94thereby increasing the reactive surface area of the gas in the gas-liquid reactionxe2x80x94no commercially viable system that works for fast and slow fluid flow rates has heretofore been developed.
The present invention comprises a method and apparatus which overcomes the foregoing and other difficulties that have long since characterized the prior art. In accordance with the broader aspects of the invention there is generated a stream of sub-micron sized gas bubbles. Due to their extremely small size, the gas bubbles have an extremely large surface area which increases reaction efficiency. Smaller pores in a gas permeable partition, i.e., pores having diameters of between about 0.1 microns and about 2 microns, facilitate the formation of smaller bubbles. Additionally, high velocity relative movement between a liquid and the partition surface aids in shearing the bubbles off the surface while they are still small.
In accordance with first, second, and third embodiments of the invention, a gas permeable tube is positioned within a glass tube and water or other liquid is caused to continuously flow through the annular space between the two tubes. Gas is directed into the interior of the gas permeable tube and is maintained at a pressure high enough to cause gas to pass into the water or other liquid and prevent the flow of water or other liquid into the interior of the gas permeable tube. As the water or other liquid passes over the gas permeable tube, gas bubbles are continually sheared off of its surface. The gas bubbles thus generated are sub-micron in size and therefore present an extremely large surface area. The gas permeable tube may also be rotated relative to the liquid.
In accordance with a fourth embodiment of the invention, there is provided a hollow disk which supports a gas permeable partition. The disk is positioned within a water or other liquid filled container. Gas is directed into the interior of the disk and is maintained at a pressure high enough to cause gas to pass outwardly through the partition and into the water or other liquid and to prevent the flow of water or other liquid into the interior of the disk. The disk and the partition are moved at high speed relative to the liquid. As the gas permeable partition moves relative to the water or other liquid, gas bubbles are continually sheared off of its surface. The gas bubbles thus generated are sub-micron in size and therefore present an extremely large surface area.
In accordance with all embodiments of the invention, the viscosity of the liquid into which the sub-micron sized gas bubbles will be produced is an inherent characteristic of the liquid. Liquids which are highly viscous will not allow for the ideal relative movement between the partition and the liquid, resulting in the poor bubble formation. However, as viscosity is proportional to temperature, one can increase the temperature of the liquid to decrease the viscosity of the liquid, overcoming this limitation.